Mobile vehicles are, in some instances, used as probes for transmitting information from an on-board telematics unit to a traffic information server. The information may include, for example, the speed that the vehicle is traveling and/or the location of the vehicle at a particular time. Similar information may also be transmitted from several other vehicles. The information from all of the vehicles may be compiled and analyzed to determine traffic conditions and to create traffic flow maps and/or traffic information services.